The invention relates to refiners intended for refining fibrous material, and to blade elements to be used therein.
Refiners intended for refining fibrous, lignocellulose-containing material are employed, for instance, for producing pulp to be used in paper or board making. Conventionally, these refiners comprise two refining surfaces opposite one another, at least one refining surface of which is arranged mobile or rotating in such a manner that the refining surfaces may move in relation to one another. One refiner, however, may also comprise several pairs of opposing refining surfaces. Between the opposing refining surfaces there is a blade gap, into which the material to be refined is fed.
WO publication 2005/032720 A1 discloses a refining surface comprising protrusion-like refining surface portions which grind the material to be refined and which are placed between groove-like refining surface portions feeding material to be refined in a blade gap and discharging refined material from the blade gap. Said refining surface portions feeding material to be refined and discharging refined material contribute to the passage of refined material in the blade gap of the refiner. The upper surface of the refining surface portions defibrating the material to be refined comprises bars, which perform the actual refining, and between them grooves, which connect said groove-like refining surface portions feeding the material to be refined and discharging the refined material. The solution disclosed in said publication provides a refining surface of large refining surface area.